Self contained powered injection system

ABSTRACT

Method and apparatus for injecting fluids into patients at a controlled rate from an ampule containing the injecting fluid with a sliding piston therein to force the fluid from the ampule into the patient using a drive system which incrementally and successively advances the piston in the ampule to meter the fluid into the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of our co-pending applications Ser. No.741,528, filed Nov. 12, 1976, now U.S. Pat. No. 4,150,672, and Ser. No.964,953, now U.S. Pat. No. 4,235,234, issued Nov. 25, 1980 and filedNov. 30, 1978.

TECHNICAL FIELD

This invention relates generally to devices for dispensing or injectinga fluid at a controlled rate and more particularly to a device for usein the medical field to inject fluids into the body of a patient at aslow rate over a prolonged period of time.

BACKGROUND ART

It is desirable in the medical profession to inject fluids such asliquid medicaments into the body of the patient, whether human oranimal, at a relatively slow rate over a prolonged period of time.Several varieties of medical treatments such as chemotherapy, pre- andpost-surgery treatments for the prevention of blood clotting, variousnutrient treatments, various antibiotic treatments and treatment ofcertain other diseases generally require low rates of injection over along period of time. Such injections are generally made intravenouslyfor subcutaneously into the patient. Some of these treatments generallyrequire that the fluid be introduced relatively continuously over anextended period of time at varying rates ranging from very slow rates,usually about 1 cc per 24-hour period, to relatively fast rates of morethan about 5 cc per 24-hour period. Because a significant increase inthe predetermined rate of injection during these continuous treatmentsmust be accurately controlled to prevent serious injury to or fatalityof the patient, the rate of injection must be frequently and closelymonitored.

There are a number of liquid dispensing or injection devices presentlyknown which attempt to dispense or inject a liquid into a patient at avery slow continuous rate over an extended period of time. These priorart injection systems, however, suffer from a number of drawbacks.

One problem frequently encountered with such prior art injection systemsis that the system cannot reliably inject small quantities of fluid overa prolonged period of time. To compensate for this inadequacy, medicalpersonnel have had to dilute the liquid medicament with neutral fluidsto reduce the unit liquid medicament concentration of the fluid beinginjected so that a relatively large quantity of fluid could be injectedwithout overdosing the patient with the active liquid medicament and sothat the undesired consequences due to variations in fluid injectionrate were minimized. This, of course, increases the weight of the fluidbeing injected and also increases the power required to inject thislarger quantity of fluid into the patient. The net result is that theoverall weight of these systems due to the weight of the fluid to beinjected and the weight of the necessary power supply is at a level thatvirtually precluded these injection systems being made sufficientlyportable for the patient to carry on his usual daily activities.

Another problem commonly found with the prior art injection systems isthat a failure in some component of the system can cause the injectionsystem to exceed the desired injection rate. This not only has resultedin the use of the diluted liquid medicament but has also requiredfrequent monitoring of the injection system by medical personnel tocompensate for this problem. To further compensate for this problem, thepatient has usually been confined to a medical facility so thatcounteractive treatment is quickly available in the event of overdosageof the patient.

SUMMARY OF THE INVENTION

According to the invention, there is provided a method of injectingfluid into a patient at an average prescribed injection rate over aprolonged period of time from a chamber carrying the fluid with anoutlet connecting the fluid to the patient and with a piston in thechamber movable toward the outlet to force the fluid into the patientcharacterized by the steps of connecting the piston to a driving meansconstructed and arranged to move the piston only a prescribed distancetoward the outlet each time the driving means is operated regardless ofthe length of time the driving means is operated to force a known volumeof the fluid into the patient each time the piston is moved theprescribed distance at an injection rate greater than the desiredaverage prescribed rate where the known volume is much less than thetotal volume of fluid to be injected over the prolonged period of time;and alternately operating and stopping the operation of the drivingmeans to cause the fluid to be injected at the average prescribed rateover the sum of the times the driving means is operated and not operatedso that, in the event of a malfunction which continuously operates thedriving means, the piston will be moved only the prescribed distancetoward the outlet to prevent overdosing the patient.

The method of the invention may be further characterized by operatingthe driving means for a fixed period of time each time the driving meansis operated and stopping the operation of the driving means for aselectively variable period of time so that the average prescribedinjection rate can be changed. The method of the invention may likewisebe further characterized by selectively varying the prescribed distancethe piston is moved each time the driving means is operated so as tovary the known volume of fluid injected each time the driving means isoperated while maintaining the period of time the driving means is notoperating constant to selectively change the average prescribedinjection rate.

The invention also includes the apparatus for carrying out the abovemethods of injecting fluid into the patient. The driving means mayinclude a solenoid, a stepping motor, or a piezoelectric device with anappropriate control means.

In summary, the invention of this application overcomes the problems anddisadvantages associated with the prior art by providing an injectionsystem which has the capability of injecting fluid slowly and preciselyinto a patient at a known, easily measurable and easily variable rate.The system is extremely fail-safe in that failure of any part of thedevice will result in disabling the device to prevent a too rapidinjection rate or any further injection of the fluid. Further, thesystem provides a human receptive indication, visible and/or audible, orwhether the device is working which can be easily and readily monitoredby the patient and/or medical personnel thereby greatly reducing thenumber and skill of medical personnel necessary to monitor the injectionrate. Because the system of the invention is able to precisely controlthe injection of the fluid, the volume and thus the weight of the fluidinjected is minimized because of its concentrated form rather thandiluted form. Also, the power required to dispense this minimized volumeof fluid is minimized to minimize the power pack weight. As a result,the system of the invention can be made highly portable so that thepatient is not hampered in his ambulatory capability thereby maximizingthe amount of productive time available to the patient even duringtreatment. Because of these features, the system of the invention isideally suited for out-patient use not presently clinically available toprevent unnecessary hospitalization and expense.

These and other features and advantages of the invention disclosedherein become more apparent upon consideration of the following detaileddescription and accompanying drawings wherein like characters ofreference designate corresponding parts throughout the several views andin which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating the invention;

FIG. 2 is an exploded perspective view illustrating the injectionapparatus of the invention;

FIG. 3 is an enlarged exploded perspective view illustrating a firstembodiment of the apparatus seen in FIG. 2 with portions thereof brokenaway to show the construction thereof;

FIG. 4 is an elevational view partly shown in cross-section of thatembodiment of the apparatus seen in FIG. 3;

FIG. 5 is an enlarged view of the ratchet mechanism of the apparatustaken along line 5--5 in FIG. 4;

FIG. 6 is enlarged view of the transmission in FIG. 4;

FIG. 7 is an enlarged view of that portion encircled by line 7 in FIG. 4and shown partly in cross-section;

FIG. 8 is an enlarged view of that portion encircled by line 8 in FIG. 4and shown partly in cross-section;

FIG. 9 is an enlarged view taken along line 9--9 in FIG. 2 showing theampule;

FIG. 10 is an enlarged cross-sectional view taken along line 10--10 inFIG. 1;

FIG. 11 is an enlarged cross-sectional view taken along line 11--11 inFIG. 1;

FIG. 12 is an electrical block diagram of the controller circuit of theinvention seen in FIGS. 1-3;

FIG. 13 is a graphic illustration of the control circuit of FIG. 12;

FIG. 14 is a view similar to FIG. 6 illustrating a modification of theinvention;

FIG. 15 is an enlarged side view taken along line 15--15 in FIG. 14;

FIG. 16 is an enlarged exploded perspective view similar to FIG. 3illustrating a second embodiment of the apparatus of the invention;

FIG. 17 is an enlarged view taken generally along line 17--17 in FIG.16;

FIG. 18 is an electrical block diagram of the controller circuit of theinvention seen in FIG. 16;

FIG. 19 is a graphic illustration of the control output of thecontroller circuit illustrated in FIG. 18;

FIG. 20 is an enlarged partial perspective view illustrating a modifiedsecond embodiment of the power unit;

FIG. 21 is an enlarged view taken generally along line 21--21 in FIG.20;

FIG. 22 is a view illustrating a first alternate embodiment of theinvention; and

FIG. 23 is a view illustrating a second alternate embodiment of theinvention.

These figures and the following detailed description disclose specificembodiments of the invention; however, it is to be understood that theinventive concept is not limited thereto since it may be embodied inother forms.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to FIG. 1, it will be seen that the fluid injection system 10includes an injector 11, a carrier 12 for mounting the injector on thepatient, and a connector assembly 14 for connecting the output ofinjector 10 to the patient, usually intravenously or subcutaneously.FIG. 2 illustrates the injector 11 in more detail. The injector 11 has apower unit 20 for selectively forcing a fluid from the ampule orcontainer 21 carrying the fluid. The ampule 21 is positioned on thepower unit 20 by an ampule holder 22. Thus, the fluid from the ampule 21is forced into the patient by the power unit 20 via the connectorassembly 14.

A first embodiment of the power unit 20 is seen in FIGS. 2-5. The powerunit 20 includes a housing 30 which removably mounts the ampule holder22 thereon about an expelling axis A_(E) (FIG. 2) as will become moreapparent. The housing 30 mounts a drive screw assembly 31 therein aboutthe expelling axis A_(E) to expel fluid from the ampule 21 carried inholder 22 as will become more apparent. The drive screw assembly 31 isdriven by a driving solenoid 32 through a transmission 34 (FIG. 3). Abattery 35 is provided to power solenoid 32 through a controller 36.

The housing 30 has a base 39 which mounts the various componentsthereon. A removable cover 38 is adapted to fit over base 39 to enclosethe components mounted on the base. Locating pins 37 maintain cover 38in alignment with base 39 and latch pin 33 keeps cover 38 in place asbest seen in FIG. 3.

The drive screw assembly 31 includes an externally threaded drive screw40 (FIGS. 2-4) which forces the fluid from ampule 21. The drive screw 40is positioned coaxially along the expelling axis A_(E) by an internallythreaded split nut 41 (FIGS. 2 and 4) mounted on the base 39 of housing30 so that nut 41 is axially fixed along axis A_(E). Nut 41 can beopened as seen by dashed lines in FIG. 2 to release the drive screw 40so that it can be manually moved axially along axis A_(E) and nut 41re-engaged as will become more apparent. With nut 41 closed to engagedrive screw 40, rotation of drive screw 40 shifts drive screw 40 axiallyalong the expelling axis A_(E). The outboard end of drive screw 40projecting outside of housing 30 is provided with a pointed drivingprojection 42 (FIGS. 2 and 9) which engages the piston in the ampule 21as will become more apparent.

The drive screw 40 is driven through a slip joint 44 (FIGS. 3, 4 and 7).The slip joint 44 is provided through a driven member 45 (FIG. 7)affixed to the inboard end of the drive screw 40. The drive screw 40defines an axially extending passage 46 therein opening onto its inboardend with the passage 46 being closed by driven member 45. The drivenmember 45 defines a noncircular driven passage 48 therethrough which isshown as being hexagonal in shape. The driven passage 48 is centered onthe expelling axis A_(E). A drive shaft 49 with a driving section 47having a cross-sectional shape complementary to the driven passage 48 ina driven member 45 slidably extends therethrough so that rotation ofdrive shaft 49 rotates the drive screw 40. The driving section 47 ondrive shaft 49 projecting through the driven member 45 is freelyreceived in the passage 46 in drive screw 40. The passage 46 extendsalong the length of drive screw 40 terminating just inboard of theprojecting end of the drive screw 40 as seen in FIG. 9 so that clearancefor the driving section 47 on drive shaft 49 is provided when drivescrew 40 is fully retracted into housing 30.

The drive shaft 49 is rotatably journalled in bearings mounted insupport plates 50 of the transmission 34 as seen in FIG. 6 so that thecentral axis of the drive shaft 49 is coaxial with the expelling axisA_(E). The journalled connections between the drive shaft 49 and thesupport plates 50 prevent axial movement of the drive shaft 49 along theexpelling axis A_(E) while allowing the drive shaft 49 to be rotatedabout the expelling axis A_(E). Thus, it will be seen that, as the driveshaft 49 is rotated clockwise as seen in FIG. 3 with the nut 41 closedabout the drive screw 40, the drive screw 40 will be rotated to axiallydisplace the drive screw 40 along the expelling axis A_(E) and move thepointed driving projection 42 on the projecting end of the drive screw40 out of the housing 30.

To retract the drive screw 40 back into the housing 30, the split nut 41is opened as shown by dashed lines in FIG. 2 and the drive screw 40manually pushed back into the housing 30 with the driving section 47 onthe drive shaft 49 sliding through the driven member 45. After the drivescrew 40 has been retracted back into the housing 30, the split nut 41is reclosed to reengage the drive screw 40 so that it can be driven backout of the housing 30 by rotating the drive shaft 49.

The transmission 34 (FIGS. 3-6) is powered by solenoid 32 to rotate thedrive shaft 49. The drive shaft 49 serves as the output of thetransmission 34 with an output spur gear 51 fixedly mounted on the driveshaft 49 between the support plates 50 so that rotation of the outputspur gear 51 rotates the drive shaft 49. The output spur gear 51 isrotatably driven by an input ratchet assembly 52 driven by the drivingsolenoid 32.

The input ratchet assembly 52 (FIGS. 3 and 5) includes a spur drivepinion 54 mounted on a pinion shaft 55 rotatably journalled between thesupport plates 50. The pinion shaft 55 also mounts thereon a ratchetmechanism 56 which includes a driven ratchet member 58 defining ratchetteeth 59 thereon about a positioning boss 60. The driven ratchet member58 is fixed to the pinion shaft 55 so that rotation of the drivenratchet member 58 also rotates the pinion shaft 55 and thus the spurdrive pinion 54. Driving ratchet member 61 is rotatably mounted aboutthe positioning boss 60 for both rotational movement about the boss 60and axial movement along the boss 60. The driving ratchet member 61includes ratchet teeth 62 thereon which are complementary to the ratchetteeth 59 on the driven ratchet member 58. The ratchet teeth 62 face theratchet teeth 59 so that, when the driven ratchet member 61 is forcedtoward the ratchet teeth 59 on the driven ratchet member 58, the ratchetteeth 62 on the driving ratchet member 61 engage the ratchet teeth 59 onthe driven ratchet member 58 whereby rotation of driving ratchet member61 counterclockwise as seen in FIG. 3 rotates the driven ratchet member58 therewith thus rotating the spur drive pinion 54. When the drivingratchet member 61 is rotated clockwise as seen in FIG. 3, the ratchetteeth 62 can slip over the ratchet teeth 59 so that the driven ratchetmember 58 can be held stationary while the driving ratchet member 61rotates with respect thereto. A ratchet spring 64 is positioned aroundthe positioning boss 60 on that side of the driving ratchet member 61opposite the ratchet teeth 59 on driven ratchet member 58 so that theratchet spring 64 constantly forces the driving ratchet member 61 towardthe teeth 59 on the driven ratchet member 58 to maintain the ratchetteeth 59 and 60 in driving engagement with each other, yet the ratchetteeth 62 on the driving ratchet member 61 can ratchet over the ratchetteeth 59 on the driven ratchet member 58 when the driving ratchet member61 is moved clockwise as seen in FIG. 3.

A ratchet clutch assembly 70 (FIGS. 3 and 5) is provided in the inputratchet assembly 52 to prevent the driven ratchet member 58 from beingrotated in a clockwise direction as seen in FIG. 3. The ratchet clutchassembly 70 includes a ratchet wheel 71 affixed to the pinion shaft 55and provided with peripheral ratchet teeth 72 which are engaged by aresilient stop member 74 best seen in FIG. 3. The ratchet teeth 72 onthe ratchet wheel 71 are oriented with respect to the resilient stopmember 74 so that the ratchet wheel 71 can rotate with the pinion shaft55 in a counterclockwise direction as seen in FIG. 3; however, theresilient stop member 74 engages the ratchet teeth 72 when an attempt ismade to rotate the pinion shaft 55 in the clockwise direction to preventthe ratchet wheel 71 and thus the pinion shaft 55 from being rotated ina clockwise direction. This serves to prevent the driven ratchet member58 and thus the spur drive pinion 54 from being rotated in a clockwisedirection as seen in FIG. 3. Because the stop member 74 is resilient, itwill be deflected over the ratchet teeth 72 as the pinion shaft 55 andratchet wheel 71 are rotated in the counterclockwise direction. Theratchet wheel 71 also serves to captivate the ratchet spring 64 betweenit and the driving ratchet member 61 so that the driving ratchet member61 is forced toward the ratchet teeth 59 on the driven ratchet member58. The ratchet wheel 71 is provided with locating flange 75 thereonwhich extends over the ratchet spring 64 to prevent inadvertentdislodgement of the ratchet spring 64.

The transmission 34 is also provided with a manually operated flushmechanism 80 (FIGS. 3, 5 and 6) which drives the output spur gear 51through the input ratchet assembly 52 to allow the drive screw 40 to bemanually rotated for flushing the injector as will become more apparent.The manually operated flush mechanism 80 includes a driven spur pinion81 affixed to the pinion shaft 55 adjacent the ratchet wheel 71 oppositethe ratchet mechanism 56. The driven spur pinion 81 meshes with amanually driven spur gear 82 journalled between one of the supportplates 50 on the transmission 34 and a subplate 84 as best seen in FIGS.3 and 6. The shaft 85 carrying the spur gear 82 extends through thesupport plate 50 and is provided with a drive slot 86 in the projectingend thereof outside of the support plate 50 so that the drive slot 86can be engaged through an appropriate opening by a manually operatedtool such as a screwdriver SD partly seen in FIG. 3 to rotate the shaft85 and spur gear 82. This rotates the driven spur pinion 81 to drive thepinion shaft 55. It will also be noted that the ratchet clutch assembly70 permits the pinion shaft 55 only to be rotated in thecounterclockwise direction as seen in FIG. 3. Thus, the shaft 85carrying the spur gear 82 can be rotated only in the clockwise directionto extend drive screw 40. Because of the gear ratio of the spur gear 82with respect to the spur pinion 81, the drive screw 40 can be relativelyrapidly extended to flush the injector 11 as will become more apparent.

Alternatively, a flush mechanism may be provided by extending theprojecting end of the drive shaft 49 through that support plate 50 mostremote from its driving section 47 and making a slot similar to slot 86in shaft 85 in the projecting end of drive shaft 49 to be engagedsimilarly to shaft 85 to manually rotate shaft 49 clockwise. This wouldeliminate the flush mechanism 80 while still providing a flushingcapability. The input ratchet assembly 52 and ratchet clutch assembly 70would permit flushing in the same manner as explained for flushmechanism 80.

The driving ratchet member 61 is provided with a driving projection 90(FIGS. 3, 5 and 6) which is used to rotate the driving ratchet member61. The movement of the driving projection 90 rotating the drivingratchet member 61 is limited by upper and lower stops 91 extending aboveand below the driving projection 90 between the support plates 50 asseen in FIG. 3. The driving projection 90 is constantly urged in aclockwise direction toward the lower stop 91 as seen in FIG. 3 by a leafspring 92 as will become more apparent.

The driving projection 90 is pivoted in counterclockwise direction asseen in FIG. 3 by a drive arm 95 pivoted on the base 39 of housing 30 at96. The drive arm 95 has a projecting end 98 which extends through aslot 99 in one of the support plates 50 to engage the driving projection90 in opposition to the leaf spring 92. The drive arm 95 also has adriving projection 100 thereon which is engaged by a driving solenoid 32to pivot the drive arm 95 clockwise as seen in FIG. 3 when the drivingsolenoid 32 is energized. This causes the projecting end 98 on the drivearm 95 to pivot the driving projection 90 counterclockwise as seen inFIG. 3 to rotate the driving ratchet member 61 counterclockwise therebydriving the drive pinion 54 counterclockwise and the output gear 51clockwise to rotate the drive screw 40 clockwise as seen in FIG. 3 andincrementally move the pointed driving projection 42 on the end of thedrive screw 40 out of the housing 30. When the driving solenoid 32 isde-energized, the leaf spring 92 pivots the driving projection 90clockwise as seen in FIG. 3 while pivoting the drive arm 95counterclockwise as seen in FIG. 3 to reset the drive for anotheradvancement of the drive screw 40.

The driving solenoid 32 is mounted on the base 39 as best seen in FIG. 3about an axis A_(S). The solenoid 32 has an open ended tubularcylindrical case 110 which mounts an actuator coil 111 therein. Acircular actuator plate 112 is pivoted to one end of the case 110 by ahinge spring member 114 so that the actuator plate 112 is magneticallyresponsive to the actuator coil 11. The actuator plate 112 is seen inits deactivated or open position in FIG. 3. Activation of the actuatorcoil 111 pivots the actuator plate 112 toward the open end of thecylindrical case 110 to its activated or closed position. The movementof the actuator plate 112 is stopped by the end of case 110. Theactuator plate 112 has an L-shaped driving projection 115 thereon with adriving section 116 coplanar with the actuator plate 112 and a checksection 118 which extends along the side of the case 110 generallyparallel to the solenoid axis A_(S). The check section 118 is providedwith a check slot 119 therein which is engaged by a check member 120adjustably mounted on the case 110 by a locking screw 121. The checkmember 120 has a check projection 122 which extends through the checkslot 119 in the driving projection 115 to limit the amount of movementof the driving projection 115 as the actuator plate 112 moves away fromthe open end of case 110 to its deactivated position. The actuator plate112 is constantly urged toward its deactivated position by theresiliency of hinge spring member 114 as well as the leaf spring 92 inthe transmission 34.

Since the movement of the actuator plate 112 toward the open end of case110 when coil 111 is energized is arrested by the end of case 110 andsince the movement of the actuator plate 112 away from the open end ofcase 110 when coil 11 is de-energized is arrested by the checkprojection 122, the amount of movement of the driving section 116 on thedriving projection 115 can thus be adjusted with the locking screw 121holding the check member 120 on the case 110. Thus, the driving section116 on the driving projection 115 is moved the adjustable distance d_(S)seen in FIG. 3 as the actuator plate 112 is moved from its deactuatedposition to its actuated position. The arcuate driving projection 100 onthe drive arm 95 extends behind the driving section 116 on the drivingprojection 115 as seen in FIG. 3 so that the closure of actuator plate112 when coil 110 is energized serves to pivot the drive arm 95clockwise as seen in FIG. 3. This in turn causes the projecting end 98on the drive arm 95 to pivot the driving projection 90 connected to thedriving ratchet member 61 to rotate the drive pinion 54 counterclockwiseand the drive shaft 49 clockwise through output spur gear 51 to screwthe drive screw 40 in the split nut 41 and move the pointed drivingprojection 42 out of the housing 30 as will become more apparent.

It will also be appreciated that the input ratchet assembly and theratchet clutch assembly may be used to connect the output spur gear 51to the drive shaft 49 rather than connecting pinion shaft 55 to inputdrive pinion 54. This is illustrated in FIGS. 14 and 15. FIG. 14corresponds generally to FIG. 6 and FIG. 15 is taken along line 15--15in FIG. 14 to show the connection between the output spur gear 51 anddrive shaft 49. The input ratchet assembly has been designated 52' andthe check clutch assembly has been designated 70' in FIGS. 14 and 15.

From FIG. 14, it will be seen that the driving projection 90 isconnected directly to the pinion shaft 55 and input drive pinion 54. Thepivoting movement of projection 90 is still limited by the stops 91,driven in a counterclockwise direction by the driving projection 98 ondrive arm 95, and urged in a clockwise direction by the leaf spring 92in the manner described above.

As seen in FIG. 15, however, the output spur gear 51 is rotatablyjournalled about the drive shaft 49 rather than being affixed thereto sothat gear 51 is free to rotate about shaft 49. The input ratchetassembly 52' serves to connect gear 51 to drive shaft 49 so thatrotation of gear 51 clockwise, when viewed in the same direction as thatseen in FIG. 3, will rotate shaft 49 but allows gear 51 to rotate in theopposite direction without rotating drive shaft 49 as will become moreapparent.

Driving ratchet member 58' is affixed to the spur gear 51 so that itrotates therewith. An internally splined driven ratchet member 61' ismounted on the drive shaft 49 between support plates 50 via anexternally splined connector 60' affixed to shaft 49. Connector 60'permits driven ratchet member 61' to slide axially along shaft 49 butrotation of driven ratchet member 61' positively rotates the drive shaft49. The ends of ratchet members 58' and 61' facing each other arerespectively provided with meshing ratchet teeth 59' and 62'. Teeth 59'and 62' are constructed so that the driving ratchet teeth 59' rotate thedriven ratchet member 61' and drive shaft 49 through driven ratchetteeth 62' when spur gear 51 is rotated clockwise when viewed as in FIG.3; however, the driving teeth 59' can slip over teeth 62' when gear 51is rotated counterclockwise so that drive shaft 49 will not be rotatedcounterclockwise. Ratchet spring 64' urges teeth 59' and 62' together tomaintain them in mesh.

The ratchet clutch assembly 70' (FIG. 15) is provided in the inputratchet assembly 52' to prevent the drive ratchet member 61' and thusdrive shaft 49 from being rotated in a counterclockwise direction whenviewed in FIG. 3. The ratchet clutch assembly 70' includes ratchet wheel71' affixed to the drive shaft 49 and is provided with peripheralratchet teeth 72' which are engaged by a resilient stop member 74'. Theratchet teeth 72' on the ratchet wheel 71' are oriented with respect tothe resilient stop member 74' so that the ratchet wheel 71' can rotatewith the drive shaft 49 in a clockwise direction when viewed as in FIG.3; however, the resilient stop member 74' engages the ratchet teeth 72'when an attempt is made to rotate the drive shaft 49 in thecounterclockwise direction to prevent the ratchet wheel 71' and thus thedrive shaft 49 from being rotated in a counterclockwise direction.Because the stop member 74' is resilient, it will be deflected over theratchet teeth 72' as the drive shaft 49 and ratchet wheel 71' arerotated in the clockwise direction. The ratchet wheel 71' also serves tocaptivate the ratchet spring 64 between it and the driven ratchet member61' so that the driven ratchet member 61' is forced toward the ratchetteeth 59' on the driving ratchet member 58'. The ratchet wheel 71' maybe provided with locating flange 75' to prevent inadvertent dislodgementof the ratchet spring 64'.

The flushing function is provided by flush mechanism 80' best seen inFIG. 15. The drive shaft 49 projects through the support plate 50opposite the driving section 47 on shaft 49 and is provided with adriving slot 86'. Engaging slot 86' with a tool such as the screwdrivermentioned for use with slot 86 in flush mechanism 80 permits the driveshaft 49 to be directly rotated clockwise as viewed in FIG. 3. Thedriven ratchet member 61' can ratchet over ratchet member 59' so thatgear 51 need not be rotated. The ratchet clutch mechanism 70' preventsrotation of shaft 49 counterclockwise.

The ampule holder 22 serves to locate the fluid ampule 21 coaxiallyabout the expelling axis A_(E) best seen in FIGS. 2, 4 and 8 with theampule 21 operatively associated with the pointed driving projection 42on the drive screw 40 as will become more apparent. The ampule holder 22has a tubular side wall 130 defining an ampule receiving chamber 131therein closed at its outboard end by end wall 132 and open at itsinboard end. The chamber 131 is sized so that the ampule 21 will justslidably fit in chamber 131 as will become more apparent. The holder 22is removably attached to housing 30 by a bayonet type connector 135.Blades 136 of connector 135 are mounted on the side wall 130 of holder22 adjacent its inboard end which cooperate with spaced apart lockingpins 138 on the base 39 of housing 30 on diametrically opposite sides ofthe split nut 41 to lock the holder 22 on housing 30 with the holdercoaxial with the expelling axis A_(E).

The holder 22 also serves to maintain the split nut 41 closed aboutdrive screw 40 as seen in FIG. 4 to insure positive threaded engagementbetween screw 40 and nut 41. The inside diameter of the side wall 130 issubstantially equal to the outside diameter of nut 41 in its closedposition so that, when the inboard end of side wall 130 is placed aroundnut 41, it is positively held closed and maintained in its closedposition until the ampule holder 22 is removed.

The ampule 21 is illustrated in FIGS. 2, 4, 8 and 9 and serves to carrythe liquid medicament which is to be injected into the patient. Ampule21 has a tubular side wall 140 with central passage 142 closed at itsoutboard end by a penetrable rubber plug 141 and open at its inboardend. The side wall 140 is of constant outside and inside diameter withan outside diameter such that it is just slidably received in chamber131 in holder 22. The length L_(A) of ampule 21 is such that ampule 21just fits in chamber 131 between the annular arresting shoulder 139(FIG. 8) in holder 22 adjacent its outboard end the split nut 41 whenholder 22 is locked in position as seen in FIG. 4.

The side wall 140 of ampule 21 has an inwardly directed lip 144 at itsoutboard end seen in FIG. 9 that engages an annular groove 145 aroundplug 141 to hold it in place. A resilient expelling piston 146 isslidably received in the central passage 142 through its open inboardend and in sealing engagement with side wall 140 to form a liquidchamber 148 between piston 146 and plug 141. The liquid medicament,usually is concentrated form, fills the liquid chamber 148. When anopening is made in the rubber plug 141 as will become more apparent, theliquid medicament in the fluid chamber 148 can be expelled by moving thepiston 146 toward the plug 141. Because the ampule side wall 140 iscoaxial with the expelling axis A_(E) when positioned by the holder 22,the piston 146 will also be positioned for movement coaxially along theaxis A_(E). This aligns the piston 146 with the drive screw 40 as willbecome more apparent.

As best seen in FIG. 9, the expelling piston 146 defines a drivingcavity 150 therein facing the driving projection 42 on the projectingend of the drive screw 40. The piston 146 has annular sealing rings 151therearound to form a sliding seal with the ampule side wall 140. Thedriving cavity 150 opens onto the inboard end of piston 146 with itsoutboard end closed by a conical, forwardly tapering driven surface 152whose apex is centered on the expelling axis A_(E). The surface 152tapers uniformly about the axis A_(E) so that the driving projection 42on the drive screw 40 is aligned with the apex of surface 152.

A conical driving plate 154 is carried in the driving cavity 150 totransfer the motion of screw 40 to piston 146. The conical driving plate154 has a conical, forwardly tapering driving surface 155 complementaryto the driven surface 152 in cavity 150 on its outboard side so that theplate 154 bears against the driven surface 152. The conical drivingplate 154 also has a like conical, forwardly tapering transfer surface156 on its inboard side facing the driving projection 42. The transfersurface 156 is aligned with the driving surface 155 so that the apex 158of the transfer surface 156 is in alignment with the pointed drivingprojection 42 on drive screw 40. Thus, the pointed projection on drivescrew 40 bears against the apex 158 of transfer surface 156 to drivepiston 146. The driving surface 155 on driving plate 154 insures thatthe piston 146 will be smoothly moved along ampule 21 without canting toexpel the liquid in the chamber 148.

The driving plate 154 is maintained in cavity 150 in piston 146 by aninwardly directed annular resilient lip 159 as best seen in FIG. 9.Because the lip 159 and piston 146 are resilient, the driving plate 154can be forced into cavity 150 past the lip. After the driving plate 154is forced into cavity 150, the lip 159 reassumes the shape shown in FIG.9 to keep plate 154 in place.

The volume of liquid medicament carried by ampule 21 is, of course,determined by the internal diameter of the side wall 140 as well as thelength L_(A) of the ampule. The size is usually selected so that someconvenient volume of liquid medicament is carried in the liquid chamber48. The side wall 140 of the ampule 21 is usually graduated to indicatethe volume therein and is illustrated as containing about 5 cc of liquidmedicament. Usually, the ampule 21 is designed to carry that volume ofliquid which is to be dispensed over a 24-hour period. Because differenttreatments require widely different volumes, it would be desirable andwithin the scope of the invention that different volumes of liquidmedicament be carried in the ampule 21, depending on the particulartreatment requirements.

The exposed surface of the penetrable rubber plug 141 enclosing the endof the ampule may be covered by a tear-off cover member 160 as seen inFIG. 9 to insure the sterility of this surface. Because the liquidchamber 148 is completely enclosed by the rubber plug 141, the ampuleside wall 140 and the piston 146, the sterility of the liquid medicamentcarried in the ampule is maintained prior to its being used.

The outlet through the penetrable rubber plug 141 in the end of theampule 21 is provided by a piercing cap assembly 165 best seen in FIGS.2 and 8 mounted in the outboard end of the ampule holder 22. Thepiercing cap assembly 165 is attached to a boss 166 on the outboard sideof the end wall 132 on holder 22 so that the piercing cap assembly 165is oriented coaxially with respect to the expelling axis A_(E). Thepiercing cap assembly 165 includes an externally threaded mount 168 thatcan be screwed into the internal threads provided in the hole throughthe boss 166. The externally threaded mount 168 has a piercing needle169 extending therethrough with a pointed end 170 projecting from themount 168 into the outboard end of the ampule receiving chamber 131along the expelling axis A_(E). The pointed end 170 of needle 169extends sufficiently far into the ampule receiving chamber 131 to insurethat the pointed end 170 pierces the penetrable rubber plug 141 in theoutboard end of the ampule 21 when the ampule 21 is pushed into place. Apenetrable needle cover 171 may be provided over the pointed end 170 ofneedle 169 so that, when the penetrable rubber plug 141 in the outboardend of the ampule 21 is forced toward the pointed end of the piercingneedle 169, the penetrable needle cover 171 will be penetrated by thepointed end 170 of the piercing needle 169 prior to the pointed end 170piercing the penetrable rubber plug 141 in the ampule 21. This is bestillustrated in FIG. 8.

An appropriate connector 172 connects the delivery tubing 174 inconnector assembly 14 to the passage 175 through the piercing needle169. Passage 175 serves as the outlet from the liquid chamber 148 of theampule 21. Thus, it will be seen that, as the piston 146 is forcedtoward the penetrable rubber plug 141, the liquid medicament in theampule 21 will be forced out through the passage 175 in the piercingneedle 169 and into the delivery tubing 174.

The delivery tubing 174 may be connected directly to the patient or maybe connected to the patient via connector assembly as seen in FIG. 1.The connector assembly 14 as seen in FIG. 1 includes a manifold block180 illustrated in more detail in FIGS. 10 and 11. The manifold block180 may be permanently or removably attached to the carrier 12. Block180 has a common delivery tube 181 therefrom to which is connected acommon intravenous injection needle assembly 182 or subcutaneousinjection needle assembly 610 for connection to the patient. Both typesof needles 182 and 610 are illustrated in FIG. 1. Subcutaneous injectionneedle assembly 610 is of the type described in our co-pendingapplication Ser. No. 964,953.

The common delivery tube 181 is in communication with a common deliverychamber 184 in block 180 through a quick disconnect 185 seen in FIGS. 10and 11. The male coupling 186 on the delivery tubing 174 from theinjector 11 is connected to a continuous injection transfer chamber 188through a check valve 189. Chamber 188 is connected to the commondelivery chamber 184 so that the fluid flows through the transferchamber 188 into delivery chamber 184 and then into the patient via tube181.

A second transfer chamber 190 may be provided in manifold block 180 toafford an additional connection point. Chamber 190 also communicateswith the common delivery chamber 184 like chamber 188. The inlet to thesecond transfer chamber 190 is also equipped with a check valve 191 topermit liquid to only enter chamber 190 for discharge out the deliverychamber 184. Chamber 190 allows a second injector of the type shownherein or of other types to be used simultaneously with injector 11. Aporous plug type metering assembly PPM from an alternate injector systemis shown in FIG. 10 by way of illustration.

It is also frequently desirable to provide short injections ofmedication to the patient with needle devices such as the hypodermicsyringe HS partly seen in FIG. 11. To accommodate these injections, themanifold block 180 is provided with cross chambers 194 best seen in FIG.11. The cross chambers 194 intersect one of the transfer chambers 188 or190 and each are provided with a penetrable plug 195 such as rubber sothat the needle HN on the syringe HS can be inserted through plug 195into one of the cross chambers 194. The syringe HS can then be used toinject unmetered fluid into the patient via the common delivery tube181. Because the block 180 is made of a strong material, the needle HNwill not penetrate same to prevent injection from the hypodermic syringeand also isolates the needle HS from the delivery tube 181.

The carrier 12 is designed for convenient attachment to the patient'sbody. It is illustrated in FIG. 1 for attachment to the patient's arm.The carrier 12 includes a wide elastic band 196 which comfortably fitsover the patient's arm without significantly affecting the patient'sblood circulation. A support pouch 198 is mounted thereon which definesa continuous injector pocket therein to receive the injector 11 therein.The continuous pocket is closed by a flap 199 with an appropriatemechanism to hold the flap closed. A cutout 200 is provided in pouch 198to allow the holder 22 on injector 11 to pass therethrough. The manifoldblock 180 is illustrated as attached to band 196.

The controller 36 serves to alternatively connect and disconnect thebattery 35 to solenoid 32 at a rate such that the desired average fluidinjection rate is maintained. The controller 36 is schematicallyillustrated in FIG. 12. Basically, the controller 36 includes a timingpulse generator 210 whose pulse output operates a switching network 211to cause the switching network 211 to alternatively connect the solenoid32 to and disconnect solenoid 32 from battery 35. The pulse output ratefrom the timing pulse generator 210 can be manually adjusted through thepulse time control 212. The pulse timer control 212 is illustrated inFIGS. 2 and 3 as three manually adjustable potentiometers althoughdifferent timer control arrangements may be used.

The pulse generator output is schematically illustrated in FIG. 13.While the output is illustrated as a square wave, it is not intended tobe limiting since a variety of wave shapes may be used that functionallyoperate the switching network 211 in the manner described. Basically,the output from generator 210 has a duty cycle where the output goes tostate A with time interval t₁ and then to state B with time interval t₂during each duty cycle. State A causes the switching network 211 toconnect the battery 35 to solenoid 32 to activate it and state B causesthe switching network 211 to disconnect battery 35 from solenoid 32 todeactivate it. The physical characteristics of solenoid 32 are such thatit takes a prescribed maximum time interval t_(s) as seen in FIG. 13after output from generator 210 goes to state A for the actuator plate112 on solenoid 32 to move to its activated or closed position. Thus,the time interval t₁ that the output from generator 210 remains in stateA is selected to be slightly longer than the maximum solenoid actuationtime interval t_(s) to insure full operation of actuator plate 112. Onthe other hand, since continued activation of solenoid 32 has no furthereffect on the movement of plate 112 after it reaches its activated orclosed position, the time interval t₁ is selected to be as short aspossible to conserve the energy of battery 35 and thus extend batterylife. Since the solenoid 32 injects a fixed amount of liquid medicamenteach time it is activated and since the pulse generator output goes tostate A once each duty cycle, varying the time period t_(DC) (FIG. 13)of each duty cycle changes the injection rate. Because of the fixedactuation time t_(s) of solenoid 32, the time interval t₁ can bemaintained constant regardless of the pulse rate of the output generator210. Thus, since about the same fixed amount of liquid medicament isexpelled from ampule 21 each time solenoid 32 is activated, the overallinjection rate can be controlled by varying the time interval t₂. Thisis done by adjusting the pulse timer control 212.

FIG. 13 graphically illustrates two pulse rates, a faster rate shown bysolid lines and a slower rate shown by dashed lines. The time intervalt₁ is the same for both rates while time interval t₂ is varied. This, ofcourse, varies the duty cycle time period t_(DC).

An indicator mechanism 213 such as lamp L seen in FIGS. 1 and 2 or anaudible sound generator may be used to provide an indication that theinjector is operating. The indicator mechanism may be activated when theoutput from generator 210 is in state A or state B. Since state A isusually shorter than state B, however, it would usually be activated inresponse to state A to extend battery life.

By appropriately selecting the components of controller 36, the gearratios of the various mechanical components of power unit 20 and thesize of ampule 21, the setting of the pulse time control 212 can be madeto correspond to the injection rate delivered. For instance, with thethree potentiometers illustrated in the control 212, the setting couldcorrespond to the injection rate to two decimal places. As an example,the setting illustrated in FIG. 3 would correspond to an injection rateof 1.95 cc per 24-hour period. This facilitates adjustment of injectionrate.

It will be appreciated that the overall gear ratio of transmission 34and the drive screw assembly 31 will be determined by the size of theampule 21, the stroke of the projecting end 98 of the drive arm 95 whensolenoid 32 is energized, and the desired incremental volume of liquidmedicament to be injected each time the solenoid 32 is energized. Simplyfor ease of monitoring, one set of parameters used was one energizedtime each minute for solenoid 32 when an injection rate of about 1 ccper 24-hour period was selected. Under these requirements and with theconstruction illustrated in FIGS. 1-9, an overall gear ratio of about229:1 was satisfactory where the drive screw 40 has 32 threads per inch.Thus, each time solenoid 32 is energized, about 0.0007 cc of liquidmedicament is dispensed.

Any conventional battery 35 may be used provided it has a sufficientvoltage output to power controller 36 and solenoid 32. The particularbattery 35 illustrated is a 9 volt transistor type alkaline battery.

To protect against the controller 36 overdosing the patient throughfailure of one or more of the components, the battery 35 may beconnected to the switching network 211 through a disabling monitornetwork 214 shown by phantom lines in FIG. 12. The disabling monitornetwork 214 is provided with a feedback circuit from the timing pulsegenerator 210 and the output of the pulse generator 210 so thatmalfunction of the timing pulse generator 210 causes the feedbackcircuit to activate the disabling monitor network 214 to cause thedisabling monitor network 214 to disconnect the battery 35 from theswitching network 211 and thus disable the solenoid 32. A motion sensormay be operatively associated with the mechanical output of the solenoid32 to provide another input to the disabling monitor network 214 sothat, if the timing pulse generator 210 generates a signal in its outputwhich should cause the switching network 211 to activate the solenoid 32and no motion is sensed in the mechanical output of the solenoid 32, thedisabling monitor network 214 disconnects the battery 35 from theswitching network 211 to disable the solenoid 32. Thus, the disablingmonitor network 214 serves to disable the solenoid 32 upon malfunctionof the timing pulse generator or the failure to obtain a mechanicaloutput from the solenoid 32 when such output should be present.

SECOND EMBODIMENT

A second embodiment of the power unit which has been designated by thenumeral 220 is seen in FIGS. 16 and 17. The power unit 220 is used inthe same manner as power unit 20 for mounting the ampule 21 in theampule holder 22 to inject fluid from the ampule into the patient viathe connector assembly 14. Attention is invited to the disclosure ofthese components hereinabove and will not be redescribed. Thosecomponents of the power unit 220 which are common with the power unit 20have the same reference numerals applied thereto. From FIG. 16, it willbe seen that the power unit 220 includes housing 230 which removablymounts the ampule holder 22 thereon about the expelling axis A_(E) aswith the first embodiment of the power unit. The housing 230 mountsdrive screw assembly 31 therein about the expelling axis A_(E) to expelfluid from the ampule 21 carried in holder 22. The drive screw assembly31 is driven by a drive motor 232 through transmission 234 and battery35 is provided to power motor 232 through a controller 236.

The housing 230 has base 39 common with power unit 20 which mounts thevarious components thereon. A removal cover 238 is adapted to fit overbase 39 to enclose components mounted on the base and has a constructionthe same as the cover 38 for the power unit 20 except that the cutoutfor the controller 236 is slightly larger in the cover 238. Like housing30 for power unit 20, locating pins 37 maintain cover 238 in alignmentwith base 39, and latch pin 33 keeps cover 238 in place.

The drive screw assembly 31 includes the externally threaded drive screw40 the same as with power unit 20 which is maintained coaxially alongthe expelling axis A_(E) by the internally threaded split nut 41 (notseen in FIG. 14), the same as with the power unit 20. Thus, the drivescrew 40 is axially moved along the expelling axis A_(E) simply byrotating the drive screw 40 with respect to the split nut 41.

The drive screw assembly 231 also is driven through slip joint 44 withdrive shaft 249 having a driving section 47 thereon the same as with thedrive shaft 49 in the power unit 20. The drive shaft 249 is rotatablyjournalled in bearings mounted in the support plates 250 of transmission234 as best seen in FIG. 16 so that the drive shaft 249 is maintainedcoaxial with the expelling axis A_(E). Similarly to drive shaft 49 ofthe power unit 20, the journal connections between the drive shaft 249and support plates 250 prevent axial movement of the drive shaft 249 onthe expelling axis A_(E) while allowing the drive shaft 249 to berotated about that axis. The drive screw 40 is retracted in the samemanner as the drive screw 40 in the power unit 20.

The transmission 234 is powered by the motor 232 to rotate the driveshaft 249 as will become apparent. The drive shaft 249 serves as theoutput of the transmission 234 with the output spur gear 51 fixedlymounted on the drive shaft 249 between the support plates 250 so thatrotation of the output spur gear 51 rotates drive shaft 249 similarly tothat described with the first embodiment of the power unit. The outputspur gear 51 is rotatably driven by an input pinion 254 mounted on aninput shaft 255 journalled between the support plates 250 of thetransmission 234. The input shaft 255 is driven by the motor 232 as willbecome more apparent so that rotation of the input shaft 255 by motor232 rotates the output spur gear 51 and thus the drive screw 40 toextend it.

The transmission 234 is provided with a manually operated flushmechanism 280 as seen in FIGS. 16 and 17 which allows the drive shaft249 to be manually rotated for flushing the injector as will become moreapparent. It will be seen that the drive shaft 249 rotatably extendsthrough the support plate 250 opposite the drive screw 40 and isprovided with a drive slot 286 in the projected end thereof outside theoutboard support plate 250 so that the drive slot 286 can be engagedthrough an appropriate opening in the cover 238 by a manually operatedtool such as a screw driver illustrated in FIG. 3 so that the driveshaft 249 can be manually rotated. This allows drive shaft 249 and thusdrive screw 40 to be manually rotated for flushing. It will also benoted that the flush mechanism 280 can be substituted for the flushmechanism 80 in power unit 20.

To insure that the drive motor 232 must rotate the output spur gear 51in a clockwise direction to always extend the drive screw 40, theratchet clutch assembly 270 seen in FIG. 17 is provided on the driveshaft 249 between the support plates 250. The ratchet clutch assembly270 includes a ratchet wheel 271 affixed to the drive shaft 249 and isprovided with peripheral ratchet teeth 272 which are engaged by aresilient stop member 274. The ratchet teeth 272 on the ratchet wheel271 are oriented with respect to the resilient stop member 274 so thatthe ratchet wheel 271 can rotate with the drive shaft in a clockwisedirection as seen in FIG. 16; however, the resilient stop member 274engages the ratchet teeth 272 when an attempt is made to rotate thedrive shaft 249 in the counterclockwise direction to prevent the ratchetwheel 271 and thus the drive shaft 249 from being rotated in acounterclockwise direction. Because the stop member 274 is resilient, itcan be deflected over the ratchet teeth 272 as the drive shaft 249 andratchet wheel 271 are rotated in a clockwise direction. Thus, the driveshaft 249 can only be rotated in the clockwise direction both by thedrive motor 232 and when it is being manually rotated through the slot286 when flushing.

The drive motor 232 is mounted on the base 39 as best seen in FIG. 16coaxially about the axis A_(S) of the input shaft 255 to transmission234. The output shaft 260 of the motor 232 is connected directly to theinput shaft 255 of transmission 234 so that rotation of output shaft 260counterclockwise as seen in FIG. 16 rotates the output spur gear 51clockwise thus rotating the drive screw 40 in the desired clockwisedirection as seen in FIG. 16. Preferably, the motor 232 is a steppingmotor which rotates its output shaft 260 through a prescribed angulardisplacement A_(DM) as seen in FIG. 16 each time the motor 232 isactivated. Thus, by selecting the appropriate gear ratio between outputspur gear 51 and the drive pinion 254, the amount of extension of drivescrew 40 each time the drive motor 232 is stepped can be selected. Thestepping motor 232 will only step through the angle A_(DM) each time itis activated regardless of the length of time it remains activated.Therefore, if the controller 236 fails while keeping motor 232activated, it will only step one increment to prevent overinjection.

The controller 236 serves to alternatively connect and disconnect thebattery 35 to drive motor 232 so that the liquid medicament from ampule21 is injected into the patient at the desired rate. The controller 236is schematically illustrated in FIG. 18. The controller 236 isselectively programmable to deliver the desired injection rate viamanually operated input switch network 300. The switch network 300includes a rate increase control switch 301 operated by rate increaseinput button 302, a rate decrease control switch 304 operated by ratedecrease input button 305, and a mode selector switch 306 operated byactuator 308. Switches 301 and 302 respectively control outputs O_(U)and O_(D) to an encoding network 310 while switch 306 allows thecontroller 236 to be programmed while in a program mode and operate themotor 232 while in an operating mode as will become more apparent.Buttons 302 and 305 as well as actuator 308 can also be seen in FIG. 16.

The encoding network 310 generates an encoding output O_(E) selectivelyadjustable through outputs O_(U) and O_(D) from switches 301 and 304which is representative of the volume of liquid medicament to bedispensed over a selected time period as will become more apparent. Theoutput O_(E) is connected to one of the inputs of mode selector switch306 and also to the input of a dosage rate logic network 311.

The dosage rate logic network 311 calculates the pulse rate required todispense the selected volume of liquid medicament represented by outputO_(E) in equal increments over the manually selected time period throughmanual adjustment of selector actuator 312 on time period selector 314.Actuator 312 is seen in FIG. 16 also. After calculating the requiredpulse rate, the regulating output O_(R) from logic network 311 adjuststhe timing pulse output O_(TP) of the timing pulse generator 315. OutputO_(TP) controls switching network 316 to connect and disconnect themotor 232 to battery 35. Because controller 236 is equally applicable tothe other embodiments of the power unit, the motor is illustrated as anelectro-mechanical driving device. The operation of the timing pulsegenerator 315 and switching network 316 may correspond to that alreadydescribed for generator 210 and switching network 211.

The mode selector switch 306 has a first position which allows thecontroller 236 to be programmed and a second position which allows theinjection rate to be monitored. In the first position, the switch 306connects the output O_(E) from the encoding network 310 to a liquidcrystal display 318 so that the amount of liquid medicament to bedispensed is visually indicated by the liquid crystal readout 319. Inthe first position, selector switch 306 also enables the rate increaseand decrease control switches 301 and 304 while disabling the timingpulse generator 315 to prevent injection during programming. Thepersonnel programming the injection rate operates switches 301 and 304to establish the desired amount of liquid medicament to be injected.Depressing input button 302 on rate increase switch 301 operatesencoding network 310 to increase the displayed output O_(E) in theliquid crystal readout 319, while depressing input button 305 on therate decrease switch 304 operates encoding network 310 to decrease thedisplayed output O_(E) in the liquid crystal readout 319.

Preferably, the encoding network 310 is constructed so that, the longerthe button 302 or 305 is depressed, the faster the displayed outputO_(E) is increased or decreased as the case may be. This allows thepersonnel to rapidly run encoding network 310 until the displayed outputO_(E) reaches the vicinity of the desired amount to be injected, releasethe button 302 or 305, and then press the appropriate button 302 or 305to finally adjust the displayed output O_(E).

After the desired amount of liquid medicament is displayed in readout319, the mode selector switch 306 is transferred to the operation modevia actuator 308. The particular mode of switch 306 may be indicated byindicator lights 313 seen in FIG. 16. The actuator 312 on time periodselector 314 has usually already been set at the desired time periodover which the amount of liquid medicament is to be injected. The timeperiods available may be appropriately changed. However, since theinjection rates are usually based on increments of a twenty-four hourperiod, it will probably be convenient to have a twenty-four hour periodand several other shorter periods. When the mode selector switch 306 isin the operation mode, the control switches 301 and 304 are disabled toprevent changing output O_(E) from encoding network 310 to the dosagerate logic network 311. The dosage rate logic network 311, based on theoutput O_(E) and the setting of the time period selector 314, calculatesthe pulse rate requirements to inject the liquid medicament into thepatient and then adjusts its regulating output O_(R) to the timing pulsegenerator 315 to cause the timing pulse generator 315 to generate theappropriate timing pulse output O_(TP) to switching network, 316 tooperate motor 232 at the required stepping rate to inject the liquidmedicament at the desired rate.

To provide a visual indication of the actual injection rate, a monitornetwork 320 is connected to the output O_(TP) from the pulse generator315 and generates a monitored output O_(M) to the liquid crystal display318 via mode selector switch 306 when it is in the operation mode. Themonitor network 320 may also be connected to the time period selector314 so that the monitored rate is adjusted for different time periods.

To protect against the controller 236 overdosing the patient, thebattery 35 is connected to the switching network 316 through a disablingmonitor network 321. The disabling monitor network 321 is provided witha feedback circuit from the timing pulse generator 315 and the outputO_(TP) of generator 315 so that, malfunction of the timing pulsegenerator 315 causes the feedback circuit to activate the disablingmonitor network 321 to cause the disabling monitor network 321 todisconnect the battery 35 from the switching network 316 and thusdisable the motor 232. A motion sensor 322 is operatively associatedwith the mechanical output of the electro-mechanical driving device toprovide another input to the disabling monitor network 321 so that, ifthe timing pulse generator 315 generates a signal in its output O_(TP)which should cause the switching network 316 to activate theelectro-mechanical driving device and no motion is sensed in themechanical output of the electro-mechanical driving device by the motionsensor 22, the disabling monitor network 321 disconnects the battery 35from the switching network 316 to disable the electro-mechanical drivingdevice. Thus, the disabling monitor network 321 serves to disable theelectro-mechanical driving device upon malfunction of the timing pulsegenerator or the failure to obtain a mechanical output from theelectro-mechanical driving device when such output should be present. Analarm device 324 may be provided to the disabling monitor network 321 toprovide an alarm that the system is malfunctioning to warn the patientand/or the personnel who is monitoring the injection of the liquidmedicament into the patient.

It will be seen that the output O_(TP) from the timing pulse generator315 and the operation of the switching circuit 316 may be the same asthat described for the first embodiment of the invention. That is, theelectro-mechanical driving device may be activated for a fixed period oftime and deactivated for a variable period of time to change theinjection rate. Thus, one duty cycle of the timing pulse generatorconsists of the fixed "on" time plus the variable "off" time. On theother hand, the duty cycle of the timing pulse generator may be changedso that it has a multiple pulse duty cycle. This type of output isillustrated in FIG. 19 and has been identified as output O_(TP) '. Curve(a) in FIG. 19 illustrates one injection rate for the electro-mechanicaldriving device while Curve (b) illustrates a greater injection rate.

Output O_(TP) ' has an "on" pulse burst PB followed by an "off" time OT.The pulse burst PB has one or more "on" pulse P_(N) with short "off"pulses P_(F) therebetween so that the electro-mechanical driving devicecan cycle. Curve (a) illustrates output O_(TP) ' with two "on" pulsesP_(N) and one "off" pulse P_(F) in pulse burst PB. Thus, it will be seenthat the electro-mechanical driving device will be operated two timesduring the pulse burst PB and then deactivated during the "off" time OT.The injection rate, then, is determined by the duty cycle time t_(DC) ¹of the output O_(TP) ' which is the pulse burst time period t_(v) ¹ plusthe "off" period time t_(F). Curve (b) illustrates output O_(TP) ' withthree "on" pulses P_(N) and two "off" pulses P_(F) in pulse burst PB.Thus, it will be seen that the electro-mechanical driving device will beoperated three times during the pulse burst PB and then deactivatedduring the "off" time OT. The injection rate, then, is determined by theduty cycle time t_(DC) ² of the output O_(TP) which is the pulse bursttime period t.sub. v² plus the "off" period time t_(F) and the injectionrate for Curve (b) is greater than that for Curve (a). One simplyincreases the injection rate by increasing the number of "on" and "off"pulses P_(N) and P_(F) in pulse burst PB. The off time period t_(F)between the pulse burst PB from the timing pulse generator 315 canremain fixed. For instance, where stepping motor 232 is used, thestepping motor 232 would step only two times between each "off" time OTin the output O_(TP) ' shown in Curve (a) while the stepping motor 232would step three times between each "off" time OT in the output O_(TP) 'shown in Curve (b) in FIG. 19.

While the liquid crystal readout 319 on the liquid crystal display 318may be changed as is appropriate, the liquid crystal readout 319 isarranged to indicate the volume of liquid medicament to be injected overthe selected time period to two decimal places with the decimal point325 being shown in FIGS. 16 and 18 on the liquid crystal readout 319.The liquid crystal readout 319 as shown in FIGS. 16 and 18 has fourintegers so that up to 99.99 cc of medicament can be programmed fordispensing into the patient.

As seen in FIGS. 20 and 21, it will be seen that a conventional electricmotor 232' may be substituted for the stepping motor 232 shown in FIGS.16 and 17. To insure that the conventional motor 232' can only drive theoutput spur gear 51 a set amount, the input shaft 255 connected to thedriving motor 232' may be provided with a mechanical stop projection256' seen in FIG. 20 which extends between upper and lower stops 258'carried on support plates 250 so that the stop projection 256' can onlyrotate with input shaft 255 back and forth between the upper and lowerstops 258'. A return spring 259' is connected between the input shaft255 and the support plates 250 so that the input shaft 255 is constantlyurged in a clockwise direction in FIG. 20. Thus, when motor 232' is notactivated, the return spring 259' urges the input shaft 255 and themechanical stop projection 256' until the stop projection 256' engagesthe lower stop 258' between the support plates 250. When the motor 232'is energized, it drives the input shaft 255 and the mechanical stopprojection 256' in the counterclockwise direction in FIG. 20 until thestop projection 256' engages the upper stop 258' to prevent furtherrotation of the input shaft 255. When the drive motor 232' isde-energized, the return spring 259' rotates the input shaft 255 back toits initial position with the stop projection 256' engaging the lowerstop 258'.

As best seen in FIG. 21, input ratchet assembly 52' already described isused on drive shaft 249 together with ratchet clutch assembly 270 sothat the output spur gear 51 drives shaft 249 when it is rotatedclockwise but can rotate back counterclockwise with input drive pinion254 without rotating drive shaft 249. The input ratchet assembly 52'function is already described and will not be repeated here. Thefunction of the ratchet assembly 270' has already been described andwill not be repeated here. It will thus be seen that the return spring259' rotates both the input drive pinion 254 and the output spur gear 51back with the input shaft 255 so that the drive motor 232' always startsfrom the same rotational position and is able to rotate the input shaftand thus the output spur gear 51 only for a prescribed angulardisplacement in order that only a known fixed amount of the liquidmedicament will be injected each time the drive motor 232' is energized.

Alternatively, it will also be appreciated that the conventional typedrive motor 232' without the projection 256', assembly 70' and ratchetassembly 52' may be used where the amount of rotation of the drive motor232' can be accurately controlled such as with a brake (not shown) sothat, each time the controller 236 is activated, the drive motor 232'will rotate through a known angle or rotation. If such a drive motor isused, it will be appreciated that the controller 236 may be adjusted sothat the pulse burst PB may be a single "on" pulse P_(N) whose timeperiod t_(V) is varied.

FIRST ALTERNATE INJECTOR

An alternate injector which has been designated by the numeral 411 isseen in FIG. 22. The injector 41 may be mounted in the carrier 12 andconnected to the connector assembly 14 for injection of liquidmedicament into the patient. The injector 411 includes an expelling unit420 and an ampule 521 which is connected to the expelling unit 420 toexpel the liquid medicament carried in the ampule 421 into the patientvia the connector assembly 14 (not shown in FIG. 22). The expelling unit420 includes an expelling piston assembly 431 which is driven by abattery 435 through a controller 436. The battery 435 is the same as thebattery described hereinbefore and the controller 436 corresponds to thecontrollers described hereinabove.

The expelling piston assembly 431 includes a housing 440 which definesan elongate cylindrical piston chamber 441 therein about an expellingaxis A_(E). The piston chamber 441 has a length L_(PC) as will becomemore apparent. The piston chamber 441 slidably mounts a magneticallyresponsive piston 442 therein for sliding movement back and forth alongthe expelling axis A_(E) within the piston chamber 441. It will also benoted that the magnetically responsive piston 442 is in sealingengagement with the piston chamber 441 and has a length L_(P) which isslightly less than one-half the length L_(PC) of the piston chamber 441as will become more apparent. Thus, it will be seen that themagnetically responsive piston 442 can be slidably moved from one end ofthe piston chamber 441 to the other. An inlet port 444 is providedthrough the housing 440 into the piston chamber 441 and is centeredalong the length of the piston chamber 441. The length L_(P) of thepiston 442 is selected so that, when the piston 442 is in either of theopposite ends of piston chamber 441, the inlet port is in communicationwith that end of the piston chamber 441 in which the piston 442 is notlocated. Thus, it will be seen that when the piston 442 is in the end ofthe piston chamber 441, fluid can be introduced into the opposite end ofthe piston chamber 441 via the inlet port 444. A pair of solenoid coils445 are wound around the housing 440 at opposite ends of the pistonchamber 441 so that when either of the solenoid coils 445 is energized,a magnetic force will be generated which urges the magneticallyresponsive piston 442 toward that end of the piston chamber 441 aroundwhich the solenoid coil 445 extends. Thus, it will be seen that thepiston 442 can be moved to one end of the piston chamber 441 byenergizing one of the solenoid coils 445 while the piston 442 can bemoved to the other end of the piston chamber 441 by energizing the othersolenoid coil 445.

Each of the opposite ends of the piston chamber 441 communicates with adischarge port 446 so that, as the piston 442 moves toward each end ofthe piston chamber 441, any liquid between the moving piston 442 and thedischarge port 446 associated with the opposite end of the pistonchamber 441 will be discharged through the discharge port 446. A checkvalve 448 is associated with each of the discharge ports 446 so that thecheck valves 448 permit liquid to flow only from the piston chamber 441out through the discharge port 446 associated therewith and not in thereverse direction. It will also be noted that the check valves 448require sufficient pressure to open them that liquid flowing into thepiston chamber 441 through the inlet port 444 will not leak out throughthe discharge port 446 in communication therewith until the piston 442is forced toward the discharge port 446 to expel the liquid. Thedischarge ports 446 from opposite ends of the piston chamber 441 areconnected to a common outlet port 449 which is connected to theconnector assembly 14 (not shown) so that the liquid discharged out ofthe discharge ports 446 by the piston 442 will be injected into thepatient.

To insure that the piston 442 is held in the ends of the piston chamber441, permanent magnets 450 may be provided in the housing 440 atopposite ends of the piston chamber 441 so that, once the solenoid coil445 has moved the piston into the end of the piston chamber 441, thepermanent magnet 450 at that end of the piston chamber 441 keeps thepiston 442 in that end of the piston chamber 441 until the solenoid coil445 associated with the other end of the piston chamber 441 is energizedto drive the piston 442 back toward the other end of the piston chamber441.

It will also be seen that an inlet check valve 451 may be provided inthe inlet port 444 to prevent fluid from being forced from within thepiston chamber 441 out through inlet port 444. While the piston 442 ismoving from one end of the chamber 441 to the other, it will be seenthat the piston 442 covers the inlet port 444 so that liquid will notflow into the piston chamber 441.

The ampule 421 is different than the ampule 21 in that the ampule 421 isflexible so it can be prefilled with a known volume of liquid medicamentto be injected into the patient. The movement of the piston 442 in thepiston chamber 441 creates a partial vacuum behind the piston 442 sothat, when the piston 442 uncovers the inlet port 444, liquid medicamentfrom the ampule 421 having its outlet connected to the inlet port 444can flow into the piston chamber 441 to be expelled when the piston 442moves back toward that end of the piston chamber 441. It would likewisebe noted that a permanent container may be provided in lieu of theampule 441 which can be filled before the injector 411 is used.

The controller 436, as already explained, would be about the same as thecontrollers described hereinbefore except that the switching networkassociated with the controller would alternatively connect the "on"pulse output from the timing pulse generator to one of the solenoidcoils 445 and then the other of the solenoid coils 445 to oscillate thepiston 442 back and forth within the piston chamber 441. Like the otherembodiments of the invention, it will be seen that the movement of thepiston 442 in either direction within the piston chamber 441 can onlyinject a prescribed volume of fluid so that prevention of overdosage tothe patient is insured.

SECOND ALTERNATE INJECTOR

An alternate injector which has been designated by the numeral 511 isseen in FIG. 23. The injector 511 may be mounted in the carrier 12 andconnected to the connector assembly 14 for injection of liquidmedicament into the patient. The injector 511 includes an expelling unit520 and an ampule 521 which is connected to the expelling unit 520 toexpel the liquid medicament carried in the ampule 521 into the patientvia the connector assembly 14 (not shown in FIG. 23). The expelling unit520 includes an expelling piston assembly 531 which is driven by abattery 535 through a controller 536. The battery 535 is the same as thebattery described hereinbefore and the controller 536 corresponds to thecontrollers described hereinabove.

The expelling piston assembly 531 includes a housing 540 which defines acylindrical piston chamber 541 therein about an expelling axis A_(E).The piston chamber 541 slidably mounts an expelling piston 542 thereinfor sliding movement back and forth along the expelling axis A_(E)within the piston chamber 541. Thus, it will be seen that the piston 542can be slidably moved from its retracted position seen in FIG. 23 towardand away from the discharge end 552 of the piston chamber 541. An inletport 544 is provided through the housing 540 into the piston chamber 541between piston 542 and discharge end 552 of chamber 541 so that, whenpiston 542 is in its retracted position, the chamber 541 between piston542 and discharge end 552 can be filled with liquid medicament via port544.

The discharge end 552 of the piston chamber 541 communicates with adischarge port 546 so that, as the piston 542 moves toward the dischargeend 552 of the piston chamber 541, liquid between the moving piston 542and the discharge port 546 will be discharged through the discharge port546. A check valve 548 is associated with discharge port 546 to permitliquid to flow only from the piston chamber 541 out through thedischarge port 546 and not in the reverse direction. It will also benoted that the check valve 548 requires sufficient pressure to open itthat liquid flowing into the piston chamber 541 through the inlet port544 will not leak out through the discharge port 546 until piston 542 isforced toward the discharge port 546 to expel the liquid. The dischargeport 546 is connected to the connector assembly 14 (not shown) so thatthe liquid discharged out of the discharge port 546 by the piston 542will be injected into the patient.

It will also be seen that an inlet check valve 551 may be provided inthe inlet port 544 to prevent fluid from being forced from within thepiston chamber 541 out through inlet port 544. While the piston 542 ismoving toward and returning from the discharge end 552 of chamber 541,it will be seen that the piston 542 covers the inlet port 544 so thatliquid will not flow into the piston chamber 541.

Ampule 521 is illustrated as the same as ampule 421 although differentconfigurations can be used. The return movement of the piston 542 in thepiston chamber 541 from discharge end 552 to its retracted positioncreates a partial vacuum between piston 542 and discharge end 552 sothat, when the piston 542 uncovers the inlet port 544 in its retractedposition, liquid medicament from the ampule 521 having its outletconnected to the inlet port 544 can flow into the piston chamber 541 tobe expelled when the piston 442 moves back toward the discharge end 552of the piston chamber 541.

To drive piston 542 back and forth within piston chamber 541, a drivingmember 554 such as quartz or the like exhibiting a piezoelectric effectis anchored to housing 540 and connected to piston 542 through anappropriate linkage 555. Because member 554 exhibits a piezoelectriceffect, a voltage imposed thereon from controller 536 causes a change ofvolume of member 554. This change of volume is transmitted to piston 542via linkage 555 to cause piston 542 to be moved toward the discharge endof chamber 541 to expel the liquid. When the voltage is removed, member554 moves piston 542 back to its retracted position for chamber 541 torefill from ampule 421. Like the other embodiments of the invention, itwill be seen that the movement of the piston 542 toward discharge end552 can only inject a prescribed volume of fluid so that prevention ofoverdosage to the patient is insured.

We claim:
 1. Apparatus for injecting fluid into a patient at an averageprescribed rate over a prolonged period of time comprising:carriagemeans defining a fluid chamber therein carrying fluid to be dispensedand an outlet from said fluid chamber connected to the patient; a pistonslidably mounted in said fluid chamber for forcing fluid from saidoutlet as said piston is moved toward said outlet; an electrical powersupply; electrically operated driving means for moving said pistontoward said outlet when said electrically operated driving means isconnected to said power supply, said electrically operated driving meansconstructed and arranged to move said piston only a prescribed distancetoward said outlet each time said electrical power supply is connectedto said electrically operated driving means regardless of the length oftime said electrical power supply is connected to said electricallyoperated driving means, said piston forcing a volume of the fluid fromsaid outlet much less than the total volume of fluid to be injected overthe prolonged period of time each time said piston is moved saidprescribed distance; and, control means for selectively connecting saidelectrical power supply to and disconnecting said electrical powersupply from said electrically operated driving means at a rate such thatfluid is injected into the patient at the desired average rate over theprolonged period of time so that, if said control means fails so as tocontinuously connect said electrical power supply to said electricallyoperated driving means, said piston will be moved only said incrementalprescribed distance toward said outlet to prevent overdosing thepatient, said control means including: switching means for selectivelyconnecting said electrical power supply to said electrically operateddriving means; timing pulse generator means for operating said switchingmeans; and programming means for selectively controlling the timingpulse rate output of said timing pulse generator, said programming meansincluding encoding means; manually operated input means for selectivelyencoding said encoding means with the volume of fluid to be injectedover a selected time period; manually adjustable time period selectormeans for selecting the time period over which the fluid is to beinjected; and dosage rate logic means operatively connected to saidencoding means, said time period selector means, and said timing pulsegenerator for calculating the required timing pulse output from saidtiming pulse generator to cause the volume of fluid encoded into saidencoding means to be injected within the time period selected in saidtime period selector means and for causing said timing pulse generatorto generate the required timing pulse output.
 2. The apparatus of claim1 wherein said electrically operated driving means is a solenoid.
 3. Theapparatus of claim 2 wherein said driving means further includes ratchetmeans operatively connecting said solenoid to said piston so that thereciprocating motion output of said solenoid moves said piston in afirst direction toward said outlet.
 4. The apparatus of claim 3 whereinsaid driving means further includes clutch means operatively connectedto said piston for permitting said solenoid to move said piston only insaid first direction.
 5. The apparatus of claim 4 wherein said drivingmeans further includes:a first threaded member carried by said housing;a second threaded member threadedly engaging said first threaded memberso that relative rotation between said threaded members causes saidsecond threaded member to be axially moved to selectively engage andmove said piston in said first direction toward the fluid outlet toforce the fluid out of the fluid outlet in said container into thepatient, said ratchet means operatively connecting said solenoid to saidsecond threaded member to effect relative rotation between said firstand second threaded members.
 6. The apparatus of claim 1 wherein saidelectrically operated driving means is a stepping motor.
 7. Theapparatus of claim 1 wherein said electrically operated driving meansincludes resettable stop means for physically limiting the amount ofmovement transmitted from said electrically operated driving means tosaid piston each time said electrically operated driving means isconnected to said electrical power supply, said resettable stop meansresetting itself while said electrically operated driving means isdisconnected from said power supply to permit further movement to betransmitted to said piston when said electrically operated driving meansis reconnected to said power supply.
 8. The apparatus of claim 7 whereinsaid control means further includes mode selector means having a firstposition selectively activating said manually operated input means, saidmanually adjustable time period selector means and said dosage ratelogic means so that the volume of fluid and the time over which thefluid is to be injected encoded in said encoding means can be changed,and disabling said timing pulse generator to prevent said timing pulsegenerator from operating said driving means; and having a secondposition disabling said input means and said time period selector meansto prevent changing the volume of fluid and the time period over whichthe volume of fluid is to be injected encoded into said encoding means,and enabling said timing pulse generator to operate said solenoid tocause the volume of fluid encoded into said encoding means to beinjected within the time period selected in said time period selectormeans and for causing said timing pulse generator to generate therequired timing pulse output.
 9. The apparatus of claim 1 wherein saidcontrol means further includes:display means for providing a visualoutput; and monitoring means operatively connecting said timing pulsegenerator means to said display means to cause said visual output ofsaid display means to be indicative of the average prescribed injectionrate.
 10. The apparatus of claim 9 wherein said display means includes aliquid crystal display.
 11. The apparatus of claim 1 wherein saidcontrol means further includes disabling means operatively connected tosaid timing pulse generator means and said switching means to cause saidswiching means to disconnect said driving means from said electricalpower supply upon malfunction of said timing pulse generator means. 12.Apparatus for injecting fluid into a patient at an average prescribedrate over a prolonged period of time comprising:carriage means defininga fluid chamber therein carrying fluid to be dispensed and an outletfrom said fluid chamber connected to the patient; a piston slidablymounted in said fluid chamber for forcing fluid from said outlet as saidpiston is moved toward said outlet; an electrical power supply;electrically operated driving means for moving said piston toward saidoutlet when said electrically operated driving means is connected tosaid power supply, said electrically operated driving means constructedand arranged to move said piston only a prescribed distance toward saidoutlet each time said electrical power supply is connected to saidelectrically operated driving means regardless of the length of timesaid electrical power supply is connected to said electrically operateddriving means, said piston forcing a volume of the fluid from saidoutlet much less than the total volume of fluid to be injected over theprolonged period of time each time said piston is moved said prescribeddistance, said driving means including:a first threaded member carriedby said housing; a second threaded member threadedly engaging said firstthreaded member so that relative rotation between said threaded memberscauses said second threaded member to be axially moved to selectivelyengage and move said piston in said first direction toward the fluidoutlet to force the fluid out of the fluid outlet in said container intothe patient; a drive member mounted in said housing coaxially with saidsecond threaded member, said drive member axially fixed with respect tosaid first threaded member and rotatable about its axis; a slip jointinterconnecting that end of said second threaded member opposite saidpiston with said drive member so that said second threaded member isaxially movable with respect to said drive member while remainingrotationally fixed with respect to said drive member whereby rotation ofsaid drive member rotates said second threaded member; an electricallyoperated solenoid; and ratchet means operatively connecting saidsolenoid to said drive member so that the reciprocating motion output ofsaid solenoid rotates said drive member and said second threaded memberto move said piston in a first direction toward said outlet; and,control means for selectively connecting said electrical power supply toand disconnecting said electrical power supply from said electricallyoperated driving means at a rate such that fluid is injected into thepatient at the desired average rate over the prolonged period of time sothat, of said control means fails so as to continuously connect saidelectrical power supply to said electrically operated driving means,said piston will be moved only said incremental prescribed distancetoward said outlet to prevent overdosing the patient, said control meansincluding:switching means for selectively connecting said solenoid toand disconnecting said solenoid from said electrical power supply;timing pulse generator means generating a timing pulse output to saidswitching means to cause said switching means to alternately energizeand de-energize said solenoid to cause the fluid to be injected into thepatient at the desired average injection rate; and programming means forselectively controlling the timing pulse rate output of said timingpulse generator to selectively change the desired average injectionrate, said programming means including encoding means; manually operatedinput means for selectively encoding said encoding means with the volumeof fluid to be injected over a selected time period; manually adjustabletime period selector means for selecting the time period over which thefluid is to be injected; and dosage rate logic means operativelyconnected to said encoding means, said time period selector means andsaid timing pulse generator for calculating the required timing pulseoutput from said timing pulse generator to cause the volume of fluidencoded into said encoding means to be injected with the time periodselected in said time period selector means and for causing said timingpulse generator to generate the required timing pulse output.
 13. Theapparatus of claim 12 wherein said control means furtherincludes:display means for generating a visually perceptive quantifiedoutput; monitoring means operatively connected to the timed pulse outputof said timing pulse generator for generating an electronic outputindicative of the average fluid injection in response to the timed pulseoutput; and mode selector means having a first position connecting saidencoding means to said display means to cause said output of saiddisplay means to be a quantification of the volume of fluid encoded insaid encoding means, activating said manually operated input means toallow the volume of fluid encoded into said encoding means to bechanged, and disabling said timing pulse generator to prevent saidtiming pulse generator from operating said solenoid; and having a secondposition disabling said input means to prevent changing the volume offluid encoded into said encoding means, enabling said timing pulsegenerator to operate said solenoid, and connecting the electronic outputof said monitoring means to said display means to cause the output ofsaid display means to be a quantification of the average fluid injectionrate in response to the timed pulse output of said timing pulsegenerator.
 14. The apparatus of claim 13 wherein said display meansincludes a liquid crystal display.
 15. The apparatus of claim 14 furtherincluding connection means intraveneously connecting said fluid outleton said container means to the patient so that the fluid is injectedinto the patient at the average prescribed fluid injection rate.
 16. Theapparatus of claim 14 further including connection means subcutaneouslyconnecting said fluid outlet on said container means to the patient sothat the fluid is injected into the patient at the average prescribedfluid injection rate.
 17. The apparatus of claim 14 wherein saidcarriage means includes an ampule assembly comprising a seamless tubularside wall defining a passage therethrough opening onto opposite ends ofsaid side wall, and a penetrable member closing one end of said passageat one end of said side wall, said piston member slidably received insaid passage from that end of said tubular side wall opposite saidpenetrable member and in sealing engagement with said tubular side wall,said tubular side wall, said piston member and said penetrable memberdefining the closed fluid chamber filled with the fluid; and saidcontainer means further including a piercing assembly defining saidfluid outlet therethrough for selectively penetrating said penetrablemember to place said fluid outlet in communication with the fluid in thefluid chamber so that, as said piston member is forced toward saidpenetrable member, the fluid will be expelled through said fluid outlet.18. The apparatus of claim 17 wherein said second threaded member, saidside wall of said ampule assembly are coaxially aligned along a commonexpelling axis; wherein said second threaded member defines a pointeddriving projection on that end facing said piston and coaxially alignedwith said expelling axis; wherein said piston includes a driven memberdefining a conical bearing surface thereon opening toward said pointeddriving projection and having an apex in registration with saidexpelling axis, said conical bearing surface angling away from saidexpelling axis with equal angles therearound so that said pointeddriving projection engages said conical bearing surface in said apex toaxially move said piston along said expelling axis with the forceexerted on said piston by said second threaded member equallydistributed circumferentially about said piston to prevent canting ofsaid piston in said ampule side wall.